Our intention in this work is to identify and measure the ocular motor disabilities that accompany each of several neurological diseases. We have developed tests of ocular motor subsystems which can reveal these disorders, their progress and their response to therapy; advanced our understanding of the mechanisms of these diseases; and gained insight into the roles of some brain structures in the control of eye movements. We are monitoring electro-oculographically the fixation, saccade, pursuit, optokinetic and vestibular system, estimating on a laboratory digital computer the parameters of these models under normal and pathological conditions. The disorders under current study are: 1) cerebellar tumors and degenerative diseases; 2) Parkinson's disease; 3) progressive supranuclear palsy; 4) parietal lobe lesions; and 5) downbeat nystagmus. In addition we are observing the oculomotor changes accompanying normal aging. BIBLIOGRAPHIC REFERENCES: Cogan, D.G., Yee, R.D., and Gittinger, J.: Rapid eye movement in myasthenia gravis. Arch. Ophthalmol. 94: 1083, 1976. Zee, D.S., Yee, R.D.: Abnormal saccades in paralytic strabismus. Am. J. Ophthalmol. 83: 112, 1977.